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Full text of "Handbook Of Chemical Engineering - I"

412
CHEMICAL ENGINEERING
It is not necessary or advisable to graduate thermometers to be used in the range 200 to 500C. into intervals smaller than 1 or 2C. The undesirability except under unusual conditions of specifying, for example, six thermometers graduated in 0.1 intervals with scale range of 25 each to cover the range 200 to 350C. instead of one instrument graduated into 1 or M cannot be too strongly emphasized.
These short range thermometers are seldom provided with ice point graduations for checking and for this reason in general cannot be standardized to even as high a degree of accuracy as thermometers divided into 1 or M intervals. Very little is to be gained therefore by attempting to read these short scale instruments to 0.05 or 0.01C. when the maximum obtainable accuracy is from 0.1 to 0.5C. The following table gives accuracy data for laboratory thermometers in the range 100 to 500C., and 212 to 1,000F.
TABLE 3
Approximate scale range	Subdivision	Probable accuracy of unstandardized thermometers	Accuracy which may be obtained if thermometer is standardized
Centigrade Scale
100 to 200C.	5	2.0	1.0
100 to 200C.	2	1.0	0.5
100 to 200C.	1	1.0	0.2
100 to 200C.	H or M	0.5	0.1
200 to 300C.	5	2.0	1.0
200 to 300C.	2	2.0	0.5
200 to 300C.	Mori	1.0	0.2
300 to 400C.	5	3.0	2.0
300 to 400C.	2	3.0	1.0
300 to 400C.	1	2.0	0.5
400 to 500C.	5	5.0	2.0
400 to 500C.	lor 2	2.0	1.0
Fahrenheit Scale
212 to 400F.	5	2.0	1.0
212 to 400F.	2	1.0	0.5
212 to 400F.	Mori	1.0	0.1
400 to 600F.	5	2.0	1.0
400 to 600F.	2	2.0	0.5
400 to 600F.	1	1.0	0.2
600 to 800F.	5	3.0	2.0
600 to 800F.	2	2.0	1.0
800 to 1,000F.	5	5.0	2.0
800 to 1,000F.	2	4.0	2.0